Nicene and Post-Nicene Fathers, Vol. V:A Treatise on the Spirit and the Letter.: Chapter 8

Attend, then, carefully, to the apostle while in his Epistle to the Romans he explains and clearly enough shows that what he wrote to the Corinthians, “The letter killeth, but the spirit giveth life,” 731
must be understood in the sense which we have already indicated,—that the letter of the law, which teaches us not to commit sin, kills, if the life-giving spirit be absent, forasmuch as it causes sin to be known rather than avoided, and therefore to be increased rather than diminished, because to an evil concupiscense there is now added the transgression of the law.